Synthesis of transition-metal adamantane salts and oxide nanocomposites, and systems and methods including the salts or the nanocomposites

ABSTRACT

A method for preparing a transition-metal adamantane carboxylate salt is presented. The method includes mixing a transition-metal hydroxide and a diamondoid compound having at least one carboxylic acid moiety to form a reactant mixture, where M is a transition metal. Further, the method includes hydrothermally treating the reactant mixture at a reaction temperature for a reaction time to form the transition-metal adamantane carboxylate salt.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationSer. No. 62/508,676 filed May 19, 2017, which is incorporated byreference herein in its entirety.

TECHNICAL FIELD

The present specification generally relates to transition-metaldiamondoid salts, to nanocomposites containing transition-metal oxidesderived from the salts, to systems and methods including the salts orthe nanocomposites, and to polymer composites including the salts or thenanocomposites.

ABBREVIATIONS

° C.=Degrees Celsius

Å=Angstroms

ACA=1-adamantane carboxylic acid

AC=adamantane carboxylate

cm=centimeter (10⁻² meter)

Co(x)-AC=cobalt adamantane carboxylate prepared from reactant mixturehaving Co²⁺ to ACA molar ratio of x:1

Co-AC=cobalt adamantane carboxylate

Cu(x)-AC=copper adamantane carboxylate prepared from reactant mixturehaving Cu²⁺ to ACA molar ratio of x:1

Cu-AC=copper adamantane carboxylate

EDX=Energy-dispersive X-ray

h=hours

HRTEM=High-resolution transmission electron microscopy

IR=Infrared

LDH=layered double hydroxide

μm =micrometer (10⁻⁶ meter)

Ni(x)-AC=nickel adamantane carboxylate prepared from reactant mixturehaving Ni²⁺ to ACA molar ratio of x:1

Ni-AC=nickel adamantane carboxylate

nm=nanometer (10⁻⁹ meter)

PXRD=Powder X-ray diffraction

SEM=Scanning electron microscopy

TEM=Transmission electron microscopy

TGA=Thermogravimetric analysis

TMO=Transition metal oxide

wt. %=Weight percent

BACKGROUND

Transition metal oxides (TMOs) are a widely studied class of oxideshaving varied electronic, optical, magnetic, chemical and mechanicalproperties. Generally, TMOs are prepared by solid state synthesismethods at high temperatures, temperatures greater than 400° C.High-temperature solid state synthesis can be cumbersome, particularlywith regard to controlling the size and shape of the resultant TMOs, andoften can result in impurities arising from the diffusion lengthbarriers of the reactants. Accordingly, significant needs exist forsynthetic methods that provide TMO materials and composites of TMOmaterials that are stable or dispersible and that enable control of sizeand shape of the TMO materials. Further ongoing needs exist for systems,methods, and composite materials that include the TMO materials.

SUMMARY

According to some embodiments, a method for preparing a transition-metaladamantane carboxylate salt is provided. The method includes mixing atransition-metal hydroxide and a diamondoid compound having at least onecarboxylic acid moiety to form a reactant mixture, where M is atransition metal and hydrothermally treating the reactant mixture at areaction temperature for a reaction time to form the transition-metaladamantane carboxylate salt.

According to further embodiments, a method for preparing a nanocompositeis provided. The method includes thermally decomposing atransition-metal adamantane carboxylate salt to form the nanocomposite.

According to further embodiments, a catalyst system is provided. Thecatalyst system includes a transition-metal adamantane carboxylate salt,a nanocomposite formed by thermally decomposing a transition-metaladamantane carboxylate salt, or a mixture of a transition-metaladamantane carboxylate salt and a nanocomposite formed by thermallydecomposing a transition-metal adamantane carboxylate salt.

According to further embodiments, a method for catalyzing a chemicalreaction between at least one first reactant and at least one secondreactant is provided. The method includes reacting the at least onefirst reactant and at least one second reactant in the presence of acatalyst system, which includes a transition-metal adamantanecarboxylate salt, a nanocomposite formed by thermally decomposing atransition-metal adamantane carboxylate salt, or a mixture of atransition-metal adamantane carboxylate salt and a nanocomposite formedby thermally decomposing a transition-metal adamantane carboxylate salt.

According to further embodiments, a method for catalyzing thedecomposition of a reactant is provided. The method includes decomposingthe reactant in the presence of a catalyst system, which includes atransition-metal adamantane carboxylate salt, a nanocomposite formed bythermally decomposing a transition-metal adamantane carboxylate salt, ora mixture of a transition-metal adamantane carboxylate salt and ananocomposite formed by thermally decomposing a transition-metaladamantane carboxylate salt.

According to further embodiments, a polymer composite is provided. Thepolymer composite includes at least one polymer or copolymer; and atleast one filler material interspersed among the at least one polymer orcopolymer to form a composite. The at least one filler material ischosen from: (a) a transition-metal adamantane carboxylate salt preparedaccording to embodiments of this disclosure; (b) a nanocompositeprepared according to embodiments of this disclosure; or (c) a mixtureof (a) and (b).

According to further embodiments, a system for removing a chemicalcompound from a fluid stream is provided. The system includes anadsorbent chosen from: (a) a transition-metal adamantane carboxylatesalt prepared according to embodiments of this disclosure; (b) ananocomposite prepared according to embodiments of this disclosure; or(c) a mixture of (a) and (b). The system also includes a vessel in whichor on which the chemical compound in the fluid stream is contacted withthe adsorbent.

According to yet further embodiments, a drilling fluid is provided. Thedrilling fluid includes at least one rheology modifier chosen from: (a)a transition-metal adamantine carboxylate salt prepared according toembodiments of this disclosure; (b) a nanocomposite prepared accordingto embodiments of this disclosure; or (c) a mixture of (a) and (b).

Additional features and advantages of the embodiments described in thisspecification will be set forth in the detailed description, whichfollows, and in part will be readily apparent to those skilled in theart from that description or recognized by practicing the embodimentsdescribed in this specification, including the detailed description,which follows, the claims, as well as the appended drawings.

It is to be understood that both the foregoing general description andthe following detailed description describe various embodiments and areintended to provide an overview or framework for understanding thenature and character of the claimed subject matter. The accompanyingdrawings are included to provide a further understanding of the variousembodiments, and are incorporated into and constitute a part of thisspecification. The drawings illustrate the various embodiments describedin this specification and together with the description serve to explainthe principles and operations of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 includes stacked PXRD patterns of (a) a cobalt adamantanecarboxylate compound formed from Co(OH)₂ and 1-adamantane carboxylicacid (ACA) with a 1.0:1 molar ratio of Co²⁺ to ACA; (b) a cobaltadamantane carboxylate compound formed from Co(OH)₂ and ACA with a 0.5:1molar ratio of Co²⁺ to ACA.

FIG. 2 includes stacked IR spectra of adamantane carboxylate compoundsformed from (a) Co(OH)₂ and ACA with a 0.5:1 molar ratio of Co²⁺ to ACA;(b) a nickel adamantane carboxylate compound formed from Ni(OH)₂ and ACAwith a 0.5:1 molar ratio of Ni²⁺ to ACA; and (c) a copper adamantanecarboxylate compound formed from Cu(OH)₂ and ACA with a 0.5:1 molarratio of Cu²⁺ to ACA.

FIG. 3 includes stacked TGA profiles of adamantane carboxylate compoundsformed from (a) Co(OH)₂ and ACA with a 0.5:1 molar ratio of Co²⁺ to ACA;(b) a nickel adamantane carboxylate compound formed from Ni(OH)₂ and ACAwith a 0.5:1 molar ratio of Ni²⁺ to ACA; and (c) a copper adamantanecarboxylate compound formed from Cu(OH)₂ and ACA with a 0.5:1 molarratio of Cu²⁺ to ACA.

FIGS. 4A-4D are SEM micrographs of a cobalt adamantane carboxylatecompound formed from Co(OH)₂ and ACA with a 0.5:1 molar ratio of Co²⁺ toACA.

FIGS. 5A and 5B are SEM micrographs of a cobalt oxide nanocompositeformed from thermal decomposition of a cobalt adamantane carboxylatecompound formed from Co(OH)₂ and ACA with a 0.5:1 molar ratio of Co²⁺ toACA.

FIGS. 6A and 6B are TEM micrographs of a cobalt oxide nanocompositeformed from thermal decomposition of a cobalt adamantane carboxylatecompound formed from Co(OH)₂ and ACA with a 0.5:1 molar ratio of Co²⁺ toACA.

FIG. 6C is a selected-area diffraction pattern of the cobaltnanocomposite of FIGS. 6A and 6B.

FIG. 6D is a HRTEM micrograph of the cobalt nanocomposite of FIGS. 6Aand 6B.

FIG. 7 shows stacked PXRD spectra of (a) a nickel adamantane carboxylatecompound formed from Ni(OH)₂ and ACA with a 0.5:1 molar ratio of Ni²⁺ toACA; and (b) a nickel oxide nanocomposite formed by thermallydecomposing the compound of (a).

FIGS. 8A-8D are SEM micrographs of a nickel adamantane carboxylatecompound formed from Ni(OH)₂ and ACA with a 0.5:1 molar ratio of Ni²⁺ toACA.

FIGS. 9A and 9B are SEM micrographs of a nickel oxide nanocompositeformed by thermally decomposing a nickel adamantane carboxylate compoundformed from Ni(OH)₂ and ACA with a 0.5:1 molar ratio of Ni²⁺ to ACA.

FIGS. 10A and 10B are bright-field TEM micrographs of a nickel oxidenanocomposite formed by thermally decomposing a nickel adamantanecarboxylate compound formed from Ni(OH)₂ and ACA with a 0.5:1 molarratio of Ni²⁺ to ACA.

FIG. 10C is a selected-area electron diffraction pattern of the nickeloxide nanocomposite of FIGS. 10A and 10B.

FIG. 10D is a HRTEM image of the nickel oxide nanocomposite of FIGS. 10Aand 10B.

FIG. 11 shows stacked PXRD spectra of (a) a copper adamantanecarboxylate compound formed from Cu(OH)₂ and ACA with a 0.5:1 molarratio of Cu²⁺ to ACA; (b) a copper adamantane carboxylate compoundformed from Cu(OH)₂ and ACA with a 1.0:1 molar ratio of Cu²⁺ to ACA; and(c) a copper oxide nanocomposite formed by thermally decomposing thecompound of (a).

FIGS. 12A and 12B are SEM micrographs of a copper adamantane carboxylatecompound formed from Cu(OH)₂ and ACA with a 0.5:1 molar ratio of Cu²⁺ toACA.

FIGS. 12C and 12D are SEM micrographs of a copper adamantane carboxylatecompound formed from Cu(OH)₂ and ACA with a 1.0:1 molar ratio of Cu²⁺ toACA.

FIGS. 13A-13D are SEM micrographs of a copper oxide nanocomposite formedby thermally decomposing a copper adamantane carboxylate compound formedfrom Cu(OH)₂ and ACA with a 0.5:1 molar ratio of Cu²⁺ to ACA.

FIGS. 14A and 14B are bright-field TEM micrographs of a copper oxidenanocomposite formed by thermally decomposing a copper adamantanecarboxylate compound formed from Cu(OH)₂ and ACA with a 0.5:1 molarratio of Cu²⁺ to ACA.

FIG. 14C is a selected-area electron diffraction pattern of the copperoxide nanocomposite of FIGS. 14A and 14B.

FIG. 14D is a HRTEM image of the copper oxide nanocomposite of FIGS. 14Aand 14B.

FIG. 15 is a PXRD spectrum of a cobalt adamantane carboxylate compoundformed from Co(OH)₂ and ACA with a 0.5:1 molar ratio of Co²⁺ to ACAdecomposed at 450° C. under H₂ atmosphere.

FIG. 16 is an IR spectrum of adamantane carboxylate compounds formedfrom Co(OH)₂ and ACA with a 0.5:1 molar ratio of Co²⁺ to ACA anddecomposed at 450° C. under H₂ atmosphere.

FIGS. 17A-17D are SEM micrographs of a cobalt oxide nanocomposite formedby thermally decomposing, at 450° C. under H₂ atmosphere, cobaltadamantane carboxylate compound formed from Co(OH)₂ and ACA with a 0.5:1molar ratio of Co²⁺ to ACA.

FIGS. 18A-18D are TEM micrographs of a cobalt oxide nanocomposite formedby thermally decomposing, at 450° C. under H₂ atmosphere, cobaltadamantane carboxylate compound formed from Co(OH)₂ and ACA with a 0.5:1molar ratio of Co²⁺ to ACA.

FIG. 19 is (a) a PXRD spectrum of a copper oxide nanocomposite formed bythermally decomposing, at 450° C. under H₂ atmosphere, copper adamantanecarboxylate compound formed from Cu(OH)₂ and ACA with a 0.5:1 molarratio of Cu²⁺ to ACA and (b) an inset image enlarged to show the PXRDpattern from 6° to 18° 2θ.

FIG. 20 is an IR spectrum of a copper oxide nanocomposite formed bythermally decomposing, at 450° C. under H₂ atmosphere, copper adamantanecarboxylate compound formed from Cu(OH)₂ and ACA with (a) a 0.5:1 molarratio of Cu²⁺ to ACA.

FIGS. 21A-21D are SEM micrographs of a copper oxide nanocomposite formedby thermally decomposing at 450° C. under H₂ atmosphere copperadamantane carboxylate compound formed from Cu(OH)₂ and ACA with a 0.5:1molar ratio of Cu²⁺ to ACA.

FIGS. 22A-22D are TEM micrographs of a copper oxide nanocomposite formedby thermally decomposing at 450° C. under H₂ atmosphere copperadamantane carboxylate compound formed from Cu(OH)₂ and ACA with a 0.5:1molar ratio of Cu²⁺ to ACA.

FIG. 23A is a dark-field electron image STEM micrograph of a copperoxide nanocomposite formed by thermally decomposing, at 450° C. under H₂atmosphere, a copper adamantane carboxylate compound formed from Cu(OH)₂and ACA with a 0.5:1 molar ratio of Cu²⁺ to ACA.

FIG. 23B is an elemental mapping of copper in the STEM micrograph ofFIG. 23A.

FIG. 23C is an elemental mapping of carbon in the STEM micrograph ofFIG. 23A.

FIG. 23D is an elemental mapping of oxygen in the STEM micrograph ofFIG. 23A.

DETAILED DESCRIPTION

The diamondoids and their derivatives have shown promise in variousapplications such as in supramolecular, petrochemical, and medicinalchemistry. Compounds prepared according to methods embodied in thisspecification unite the chemistries of transition-metal oxides (TMOs)and diamondoids to form materials such as salts and nanocompositesincorporating transition metals or their oxides.

As used in this specification, the term “transition metal” refers toelements in periods 4, 5, and 6 and groups 4-12 of the periodic table ofthe elements, as defined by IUPAC in the 1990 edition of Nomenclature ofInorganic Chemistry.

As used in this specification, the term “diamondoid” refers to anychemical compound containing at least one adamantane moiety.

Reference will now be made in detail to embodiments of methods forpreparing transition-metal adamantane carboxylate salts andnanocomposites that are derived from the transition-metal adamantanecarboxylate salts and contain transition-metal oxide particles.

Methods for preparing a transition-metal adamantane carboxylate saltinclude mixing a transition-metal hydroxide and a diamondoid compoundhaving at least one carboxylic acid moiety to form a reactant mixture.

In the reactant mixture, the transition-metal hydroxide may be acompound of the formula M(OH)_(x), where M is a transition metal and xis equal to the oxidation state of the transition metal. In someembodiments, the transition-metal hydroxide may be chosen from compoundsof the formula M(OH)₂, where M is a transition metal in a +2 oxidationstate. In some embodiments, the transition-metal hydroxide may be chosenfrom compounds of the formula M(OH)₂, where M is chosen from Co, Cu, andNi.

In the reactant mixture, the diamondoid compound has at least onecarboxylic acid moiety. In some embodiments, the at least one carboxylicacid is bonded to any non-bridgehead carbon atom of the diamondoidcompound. In some embodiments, the diamondoid compound may be chosenfrom carboxylic acids of adamantane, diamantane, or triamantane. In someembodiments, the diamondoid compound may be adamantane 1-carboxylic acid(ACA).

The mixing of the transition-metal hydroxide and the diamondoid compoundmay be performed by any suitable method using any suitable apparatus toaccomplish intimate mixing. For example, the mixing may be performedusing solid-state techniques such as blending or grinding of drypowders. The mixing may be performed with the aid of an aqueous ororganic solvent by combining powders and the solvent and subsequentlystirring the resultant solution. Optionally, after such a wet mixingprocedure, some or all of the solvent may be decanted or filtered fromthe resultant mixture before the transition-metal hydroxide and thediamondoid compound are placed under conditions suitable for theirchemical reaction.

The methods for preparing a transition-metal adamantane salt furtherinclude hydrothermally treating the reactant mixture of thetransition-metal hydroxide and the diamondoid compound at a reactiontemperature for a reaction time to form the transition-metal adamantanesalt. Hydrothermal treatment generally may include adding an aqueoussolvent such as water to the reaction mixture, sealing the reactionmixture in a reaction vessel such as an autoclave, and heating thereaction vessel to the reaction temperature to cause crystallization ofthe transition-metal adamantane salt to occur in a high-pressureenvironment.

The reaction temperature is chosen to provide sufficient thermodynamicenergy for the reaction of the transition-metal hydroxide and thediamondoid compound to proceed within the reaction vessel while alsoenabling crystallization of the transition-metal adamantane salt. Thereaction temperature should be sufficiently high to enable the reactionto progress but also be sufficiently low to avoid decomposition of theadamantane salt or solvation of crystallites. In some embodiments, thereaction temperature may be from 100° C. to 200° C., such as 100° C.,110° C., 120° C., 130° C., 140° C., 150° C., 160° C., 170° C., 180° C.,190° C., 200° C., or any other temperature between 100° C. and 200° C.Though in some embodiments the reaction temperature may be from 100° C.to 200° C., it is contemplated that other reactions may occur attemperatures lower than 100° C. or higher than 200° C. In otherembodiments, the reaction temperature may be from 100° C. to 150° C. orfrom 110° C. to 150° C. In one example, where the transition metalhydroxide is Co(OH)₂ or Cu(OH)₂, the reaction temperature may be 110°C.±10° C. In another example, where the transition metal hydroxide isNi(OH)₂, the reaction temperature may be 150° C.±10° C.

The reaction time is chosen to provide sufficient time for crystalgrowth and development of well-defined morphologies to occur as thetransition-metal adamantane salt is formed at the reaction temperature.In some embodiments, the reaction time may be longer than 12 h, such asfrom 12 h to 72 h, from 24 h to 72 h, from 12 h to 48 h, or from 24 h to48 h, for example. Though in some embodiments the reaction time may belonger than 12 h, it is contemplated that when higher reactiontemperatures greater than 150° C. are chosen, for example, the reactiontime may be shorter than 12 h.

The methods for preparing a transition-metal adamantane carboxylate saltmay further include isolation steps such as cooling or depressurizingthe reaction vessel, removing the reaction mixture from the reactionvessel, removing solvent from the reaction mixture by filtering or anyother suitable technique, washing the transition-metal adamantanecarboxylate salt with an aqueous or organic solvent that does notdissolve the transition-metal adamantane salt, drying thetransition-metal adamantane carboxylate salt, or any combination ofthese steps. In some embodiments, the transition-metal adamantanecarboxylate salt may be vacuum filtered from any solvent present in thereaction vessel, washed with water, and dried at a suitable temperaturefor a suitable time. For example, the transition-metal adamantanecarboxylate salt may be dried at 65° C. for 24 h to drive off residualsolvent from the hydrothermal treatment.

The transition-metal adamantane carboxylate salt prepared using atransition-metal hydroxide M(OH)₂ and ACA will be subsequently describedby a shorthand notation M(x)-AC, where M is a transition metal, x is theratio of M and ACA in the reaction mixture used to prepare thetransition-metal adamantane carboxylate salt, and AC represents thecarbon support derived from the adamantane moiety of the ACA. Forexample, Co(0.5)-AC represents a cobalt adamantane carboxylate saltprepared by reacting Co(OH)₂ and ACA with a 0.5:1 molar ratio of Co²⁺ toACA. Likewise, Co(1.0)-AC represents a cobalt adamantane carboxylatesalt prepared by reacting Co(OH)₂ and ACA with a 1.0:1 molar ratio ofCo²⁺ to ACA. Likewise, Ni(0.5)-AC represents a nickel adamantanecarboxylate salt prepared by reacting Ni(OH)₂ and ACA with a 0.5:1 molarratio of Ni²⁺ to ACA. Likewise, Cu(0.5)-AC represents a copperadamantane carboxylate salt prepared by reacting Cu(OH)₂ and ACA with a0.5:1 molar ratio of Cu²⁺ to ACA. Likewise, Cu(1.0)-AC represents acopper adamantane carboxylate salt prepared by reacting Cu(OH)₂ and ACAwith a 1.0:1 molar ratio of Cu²⁺ to ACA.

In some embodiments, the reaction mixture may be prepared by mixing atransition metal hydroxide compound of formula M(OH)₂, where M is Co,Ni, or Cu, and ACA in amounts that provide a ratio of M²⁺ to ACA in thereaction mixture of from 0.5:1 to 1.0:1. The specific ratio of M²⁺ toACA in the reaction mixture may be chosen to affect the overall crystalmorphology of the transition-metal adamantane salt to a desired form.Without intent to be bound by theory, it is believed that the crystalmorphology of the transition-metal adamantane salt may be tailored byincreasing or decreasing the ratio of M²⁺ to ACA in the reactionmixture. Though in some embodiments the ratio of M²⁺ to ACA may beselected from 0.5:1 to 1.0:1, it is contemplated that the crystalmorphology of the transition-metal adamantane salt may be furthertailored by decreasing the ratio of M²⁺ to ACA to less than 0.5:1 or byincreasing the ratio of M²⁺ to ACA to greater than 1.0:1. Even so, apoint of saturation is believed to exist; once the point of saturationis achieved additional transition-metal ions cannot be incorporated intothe transition-metal adamantine carboxylate salt.

Further embodiments of this specification are directed to methods forpreparing nanocomposites. The methods for preparing the nanocompositesinclude thermally decomposing a transition-metal adamantane carboxylatesalt prepared according to the methods previously described in thisspecification. In some embodiments, the nanocomposites includetransition-metal oxide particles or structures supported on a carbonframework derived from the diamondoid compound.

In some embodiments, thermally decomposing the transition-metaladamantane carboxylate salt may include heating the transition-metaladamantane carboxylate salt. The heating of the transition-metaladamantine carboxylate salt may be conducted, for example, in air or areducing atmosphere at a decomposition temperature for a decompositiontime. The decomposition temperature and the decomposition time may beselected to result in complete decomposition of the transition-metaladamantane carboxylate salt. Complete decomposition of thetransition-metal adamantine carboxylate salt may include conversion ofany transition-metal hydroxide functionalities in the adamantanecarboxylate salt to transition-metal oxide particles. Suitabledecomposition temperatures may be greater than 200° C., greater than300° C., greater than 400° C., or greater than 500° C., for example. Thedecomposition time may be chosen as any time sufficient to result incomplete decomposition of the transition-metal adamantane carboxylatesalt at the chosen decomposition temperature. For example, thedecomposition time may be longer than 1 h, such as 2 h, 3 h, 4 h, orlonger than 5 h. In example embodiments, transition-metal adamantinecarboxylate salts formed from M(OH)₂ and ACA, where M is Co, Ni, or Cu,may decompose fully at a decomposition temperature of about 450° C. anda decomposition time of at least 4 h.

The reducing atmosphere for the thermal decomposition of thetransition-metal adamantane carboxylic salt is an atmospheric conditionin which oxidation is prevented by removal of oxygen and other oxidizinggases or vapors, and which may contain actively reducing gases such ashydrogen, carbon monoxide, and gases such as hydrogen sulfide that wouldbe oxidized by any present oxygen. In some embodiments, the reducingatmosphere is hydrogen gas (H₂).

Nanocomposites formed by thermally decomposing the transition-metaladamantane carboxylate salts may exhibit a variety of crystalmorphologies that may depend on variables such as the ratio oftransition-metal hydroxide to diamondoid compound in the reactionmixture used to form the transition-metal adamantane carboxylate salt,the reaction time and temperature used to form the transition-metaladamantine carboxylate, and the decomposition conditions used to formthe nanocomposite itself.

In some embodiments, the methods for preparing nanocomposites includethermally decomposing transition-metal adamantane carboxylate saltsprepared by reacting transition-metal hydroxides M(OH)₂ and ACA, where Mis chosen from Co, Ni, and Cu. Nanocomposites formed from suchtransition-metal adamantane carboxylate salts may includetransition-metal oxide particles MO_(x) of a particular shape ormorphology dispersed on a carbon support of a particular shape ormorphology. For example, in embodiments where M is Co, the metal oxideparticles may include CoO, Co₃O₄, or a mixture of CoO and Co₃O₄. Inembodiments where M is Ni, the metal-oxide particles may include NiO. Inembodiments where M is Cu, the metal-oxide particles may include CuO,Cu₂O, or a mixture of CuO and Cu₂O. The metal-oxide particle may bespherical, rectangular, ribbon-like, or in the form of nanowires,nanorods, or nanowhiskers, for example. The transition-metal oxideparticles may have particle sizes from 10 nm to 20 nm, for exampleLikewise, the carbon support may exhibit a morphology such as a sheet, ananorod, a nanowire, or a nanowhisker.

The term “nanorod” means a nanoobject having at three dimensions from 1nm to 100 nm and an aspect ratio (length divided by width) of from 3 to20, or from 3 to 10, or from 3 to 5. The term “nanowire” means aconducting anisotropic quasi-one-dimensional structure having a diameterof about 1 nm to 10 nm and a ratio of length to width greater than 1000.The term “nanowhisker” means a filamentary crystal (whisker) withcross-sectional diameter from 1 nm to 100 nm and length to diameterratio greater than 100.

In some embodiments, the transition-metal oxide particles may beuniformly dispersed over a surface of a carbon support derived from theadamantane moieties of the transition-metal adamantane carboxylate salt.The weight fraction of metal-oxide particles and carbon support may varyin the nanocomposite, depending on the conditions used to prepare thenanocomposite. In some embodiments, the nanocomposite may include from50 wt. % to 90 wt. % metal oxide particles and from 10 wt. % to 50 wt. %carbon, based on the total weight of the nanocomposite. For example, thenanocomposite may include from 70 wt. % to 80 wt. % metal oxideparticles and from 20 wt. % to 30 wt. % carbon, based on the totalweight of the nanocomposite.

In some embodiments, the nanocomposite may be formed by thermallydecomposing a cobalt adamantane carboxylate salt (Co-AC) prepared aspreviously described. Examples of such nanocomposites may have amicroporous matrix and crystallites of cobalt oxide interspersed withinthe microporous matrix. The microporous matrix may include carbonderived from the adamantane moieties of the cobalt adamantanecarboxylate salt.

In some embodiments, the nanocomposite may be formed by thermallydecomposing a nickel adamantane carboxylate salt (Ni-AC) prepared aspreviously described. Examples of such nanocomposites include porousnanowhiskers of nickel oxide particles connected to a carbon supportderived from the adamantane moieties of the nickel adamantanecarboxylate salt.

In some embodiments, the nanocomposite may be formed by thermallydecomposing a copper adamantane carboxylate salt (Cu-AC) prepared aspreviously described. Examples of such nanocomposites may have amicroporous matrix and crystallites of copper oxide supported on carbonsheets. The carbon sheets may include carbon derived from the adamantanemoieties of the copper adamantane carboxylate salt.

Further embodiments of this specification are directed to catalystsystems. The catalyst systems may include (a) a transition-metaladamantine carboxylate salt prepared according to any embodimentpreviously described; (b) a transition-metal oxide particle supported oncarbon prepared according to any embodiment previously described, suchas by thermal decomposition of a transition-metal adamantine carboxylatesalt; or (c) any catalytically active mixture of (a) and (b).

Accordingly, further embodiments of this specification are directed tomethods for catalyzing a chemical reaction between at least one firstreactant and at least one second reactant. Such methods may includereacting the at least one first reactant and at least one secondreactant in the presence of a catalyst system previously described. Theat least one first reactant and the at least one second reactant may beany chemical compounds, the chemical reaction of which is catalyticallyfacilitated, such as by being made thermodynamically possible or morefavorable, or kinetically influenced by the presence of thetransition-metal adamantane carboxylate salt or the nanocompositeseparately or in combination. In example embodiments, the chemicalreaction may be an alcohol oxidation or a cross-coupling reaction thatforms at least one carbon-nitrogen bond.

Still further embodiments of this specification are directed to methodsfor catalyzing the decomposition of a reactant. Such methods may includedecomposing the reactant in the presence of a catalyst system previouslydescribed. The decomposing of the reactant may be conducted under milderconditions than those generally known to decompose the reactant, such asunder a decreased decomposition temperature, a decreased decompositiontime, or a decreased decomposition pressure.

Still further embodiments of this specification are directed to polymercomposites that contain at least one polymer or copolymer in combinationwith at least one filler compound interspersed among the at least onepolymer or copolymer to form a composite. In such embodiments, the atleast one filler compound may be chosen from (a) a transition-metaladamantane carboxylate salt prepared according to any embodimentpreviously described; (b) a transition-metal oxide particle supported oncarbon prepared according to any embodiment previously described, suchas by thermal decomposition of a transition-metal adamantane carboxylatesalt; or (c) any mixture of (a) and (b).

Still further embodiments of this specification are directed to systemsfor removing a chemical compound from a fluid stream such as a liquidstream, a gas stream, or a slurry containing a liquid and a solid. Thesystems may include an adsorbent chosen from: (a) a transition-metaladamantane carboxylate salt prepared according to any embodimentpreviously described; (b) a transition-metal oxide particle supported oncarbon prepared according to any embodiment previously described, suchas by thermal decomposition of a transition-metal adamantane carboxylatesalt; or (c) any mixture of (a) and (b). The systems may further includeany suitable vessel in which, or any active surface on which, thechemical compound in the fluid stream is contacted with the adsorbent soas to be adsorbed onto the adsorbent and removed from the fluid stream.

Still further embodiments of this specification are directed to drillingfluids, such as a drilling fluid appropriate for use in the petroleumindustry. Such drilling fluids may include at least one rheologymodifier chosen from (a) a transition-metal adamantane carboxylate saltprepared according to any embodiment previously described; (b) atransition-metal oxide particle supported on carbon prepared accordingto any embodiment previously described, such as by thermal decompositionof a transition-metal adamantane carboxylate salt; or (c) any mixture of(a) and (b).

Thus, embodiments of transition-metal diamondoid salts, nanocompositesof carbon-supported transition-metal oxide particles have beendescribed, along with further embodiments of catalytic systems andmethods, polymer composites, systems for removing chemical compoundsfrom fluid streams, and drilling fluids incorporating one or more of thetransition-metal diamondoid salts or nanocomposites. In exampleembodiments, 1-adamantane carboxylate was used as a structure directingagent to generate the transition metal compounds having variedmorphologies. The thermal decomposition or calcination of such compoundsresults in an in situ generation of carbon-supported transition-metaloxides.

EXAMPLES

The embodiments described in the Detailed Description will be furtherclarified by the following Examples. It should be understood that thefollowing Examples are not intended to limit the scope of thisdisclosure or its claims to any particular embodiment.

As described in Examples 1, 3, and 5, transition-metal adamantanecompounds according to embodiments of this disclosure were prepared byhydrothermally treating a transition-metal hydroxide with 1-adamantanecarboxylic acid (ACA). In the following example preparations, a metalhydroxide and adamantane carboxylic acid were stirred for 1 h beforebeing transferred into a reaction vessel. The resultant mixture washydrothermally treated at different temperatures for 24 h. The resultantproducts were vacuum filtered and washed with copious amount of water,then dried at 65° C. for 24 h.

As described in Examples 2, 4, and 6, transition-metal oxides wereprepared from the transition-metal adamantane compounds by thermallydecomposing the adamantane compounds at 450° C. for 4 h under airatmosphere. Products were characterized by powder X-ray diffraction(PXRD), infra-red (IR) spectroscopy, scanning electron microscopy (SEM),thermogravimetric analysis (TGA), and transmission electron microscopy(TEM).

As described in Examples 7 and 8, additional transition-metal oxideswere prepared from the transition-metal adamantane compounds bythermally decomposing the adamantane compounds at 450° C. for 4 h underH₂ atmosphere. Products were characterized by powder X-ray diffraction(PXRD), infra-red (IR) spectroscopy, scanning electron microscopy (SEM),thermogravimetric analysis (TGA), and transmission electron microscopy(TEM).

Example 1 Synthesis and Characterization of Cobalt Adamantanes

Co-adamantane carboxylate salts (Co-AC) were synthesized by treatingCo(OH)₂ and 1-adamantane carboxylic acid (ACA) under hydrothermalconditions at 110° C. for 24 h. Prior to the reaction, the reactantswere intimately mixed by stirring for 1 h using a magnetic stirrer. TwoCo-AC compounds were synthesized with different molar ratios of Co²⁺ toACA to evaluate the effects of supersaturation on phase formation andthe morphology of the resultant phase. A first compound, Co(0.5)-AC, wassynthesized using a 0.5 molar ratio of Co²⁺ to ACA. A second compound,Co(1.0)-AC, was synthesized using a 1.0 molar ratio of Co²⁺ to ACA. Thecompounds were characterized using various analytical techniques.

The PXRD pattern of Co(0.5)-AC is provided as spectrum (a) of FIG. 1.Low angle reflections were observed at 2θ angles of 4.27°, 6.08°, 6.65°,7.50°, 9.31°, and 10.91°. These low-angle reflections indicated-spacings of 20.67 Å, 14.52 Å, 13.28 Å, 11.77 Å, 11.50 Å, and 8.1 Å,respectively. The Co(0.5)-AC showed several reflections with variedintensities up to a 2θ angle of 65°.

The IR spectrum of Co(0.5)-AC is provided as spectrum (a) of FIG. 2,which shows various distinct stretching and bending vibrations. Thevibrations at 2904 cm⁻¹ and 2846 cm⁻¹ arise from stretching modes of C—Hof the adamantane ion. Symmetric and antisymmetric vibrations of theCOO⁻group of adamantane are seen at 1508 cm⁻¹ and 1422 cm⁻¹. Themultiple stretching and bending modes less than 1000 cm⁻¹ arise frommetal-oxygen bonds. The hydroxyl ion region 3200 cm⁻¹ to 3700 cm⁻¹ isnearly featureless, indicating an absence of hydroxyl ions in thecompound. The vibration at around 1603 cm⁻¹ may arise from the bendingmode of water molecules in Co-AC.

The thermal stability of the Co(0.5)-AC was studied under N₂ atmospherefrom 25° C. to 800° C. using TGA. The Co(0.5)-AC shows a two-step massloss as shown in plot (a) of FIG. 3. The material was found to be stableup to 100° C. without losing any mass. The material lost about 22 wt. %of its mass in the range 100° C. to 180° C., which could include looselybound water molecules along with some other residues, believed to becomponents of the adamantane moiety. The material was stable from 180°C. to 400° C. with negligible amount of mass loss and then it lostaround 65 wt. % of its mass in the second step (400° C. to 550° C.). Asmall and steady mass loss was apparent from 550° C. to 800° C., and thematerial completely decomposed at 800° C. The Co-AC lost around 85 wt. %of mass from 25° C. to 800° C., indicating the formation of nanoporousoxides of cobalt. The TGA of the Co(0.5)-AC shows that Co(0.5)-AC is nota high-temperature stable phase but could be a precursor for nanoporousoxides of cobalt. The significant mass loss of around 85 wt. % indicatesthat the Co-AC is made up of a large amount of decomposable adamantanemoiety.

The morphology of the Co(0.5)-AC was characterized by SEM, as shown inFIGS. 4A and 4B. Co-AC shows an interesting fibrous nature, with eachfiber being interconnected with an adjacent one, resulting in theformation of spheres of fibers. It is believed that the adamantanebackbone may be the reason for the tendency to form spheres.

Co²⁺ has the tendency to form a-hydroxides and hydroxy salts withvarious inorganic/organic anions. Both these compounds are made up ofhydroxide layers, exhibiting interlayer chemistry. The anionsintercalated in the interlayer mediate the various properties of thesecompounds. Similarly, Co(0.5)-AC would have adopted one of these twostructures by using adamantane carboxylate ion as anion. The data fromIR spectrum clearly shows the absence of the OH⁻ ion, ruling out thecrystallization of Co-AC in an α-hydroxide/hydroxy salt structure.Considering all the data from PXRD, IR, TGA, and SEM it its believedthat the Co-AC may have a structure of Co²⁺ binding with two carboxylateions of two adamantane carboxylic acid molecules, which together form asalt of cobalt having a layered structure.

The effect of supersaturation on the formation of Co-AC was evaluated bypreparing a sample of Co(1.0)-AC using the same synthetic route aspreviously described for Co(0.5)-AC with reduction of the amount of1-adamantane carboxylate to begin with a 1:1 molar ratio of Co²⁺ to ACA.

The PXRD pattern of Co(1.0)-AC is provided as plot (c) of FIG. 1.Similarly to the Co(0.5)-AC sample, the Co(1.0)-AC was found to exhibitlow-angle reflections at 2θ angles of 3.96°, 6.4°, 8.35°, and 12.77°.These low-angle reflections indicate d-spacings of 22.3 Å, 13.8 Å, 10.58Å, and 6.9 Å, respectively. The intensity of the reflections were muchstronger for Co(1.0)-AC than in Co(0.5)-AC (see plot (a) of FIG. 1),indicating better crystal growth in case of Co(1.0)-AC. The PXRD ofCo(1.0)-AC was expected to show some unreacted Co(OH)₂, because cobaltwas in excess in the reaction mixture. An absence of reflectionsattributable to Co(OH)₂ suggests that the Co(OH)₂ may have dissolved inthe reaction medium or was obscured under the background in the PXRD.

The morphology of the Co(1.0)-AC was characterized by SEM and isillustrated in FIGS. 4C and 4D. The Co(1.0)-AC exhibited a similarmorphology to that of Co(0.5)-AC. The SEM also shows hexagonally facetedcrystals, believed to be unreacted Co(OH)₂.

Example 2 Cobalt Oxide from Thermal Decomposition of Cobalt AdamantaneCarboxylate Salts

The Co(0.5)-AC, on calcination is expected to give Co₃O₄/CoO supportedon the carbon residue of adamantane. Co(0.5)-AC prepared according toExample 1 was decomposed at 450° C. for 4 h under air atmosphere.

The PXRD of the resultant oxide material is provided as plot (b) ofFIG. 1. The PXRD showed reflections at 2θ angles of 19.23°, 31.63°,37.13°, 38.9°, 45.1°, 55.91°, and 59.63°. These reflections indicated-spacings of 4.61 Å, 2.82 Å, 2.41 Å, 2.31 Å, 2.0 Å, 1.64 Å and 1.54 Å,respectively. The reflections of the prepared sample were determined tobe more consistent with literature reports of Co₃O₄ rather than of CoO.A broad hump centered around 14° in the PXRD of the oxide sample couldnot be assigned to any phase of cobalt oxide. The origin of this broadhump is believed to arise from residual carbon present in the samplethat creates a layered material.

The oxide residue of Co(0.5)-AC was further characterized using SEM. Asillustrated in FIGS. 5A and 5B, the resultant oxide was found by SEM tohave a microporous, sponge-like morphology. The oxide crystallites werefound to grow as nanowires, which in turn form a highly porous networkhaving very large pores.

The EDX technique was used to establish the presence of the carbon inthe oxide obtained from Co-adamantane carboxylate salt decomposition. Toavoid interference of the substrate carbon with the carbon in thesample, a silicon wafer was used as a substrate during the SEM. Asexpected, the EDX analysis showed peaks attributable to Co²⁺, Co³⁺ andoxygen from the cobalt oxide. In addition, the EDX showed a peakattributable to the elemental carbon, thus indicating the presence of asignificant amount of carbon in the sample. To assess the distributionof the carbon in the cobalt oxide, elemental mapping was carried outusing an SEM/EDX technique. Within the elemental mapping, the carbon wasfound to be spread uniformly across the whole of oxide residue.

The size and shape of the cobalt oxide crystallites were characterizedby TEM (FIGS. 6A-6D). The cobalt oxides were observed to havecrystallite sizes in the range of 10 nm to 20 nm, as shown bybright-field TEM images (FIGS. 6A and 6B). The selected area diffractionpattern shows multiple diffraction rings matching with the d-spacing ofCo₃O₄ (FIG. 6C). The lattice fringes of the cobalt oxide were observedby HRTEM (FIG. 6D).

Example 3 Synthesis and Characterization of Nickel AdamantaneCarboxylate Salts

Ni-adamantane carboxylate (Ni-AC) was synthesized by treating Ni(OH)₂and 1-adamantane carboxylic acid in a 0.5:1 molar ratio of Ni²⁺ to ACA,under hydrothermal conditions at 150° C. for 24 h. Prior to thereaction, the reactants were intimately mixed by stirring for 1 h usinga magnetic stirrer. The resultant material, Ni(0.5)-AC, wascharacterized by PXRD, IR, TGA, and SEM.

The PXRD spectrum of Ni(0.5)-AC in plot (a) of FIG. 7 exhibited a seriesof lower-angle reflections at 2θ angles when compared to NiO in plot (b)of FIG. 7. The low-angle reflections at 2θ angles were 5.33°, 6.11°,6.32°, and 7.87°. These low-angle reflections indicated d-spacings of16.56 Å, 14.45 Å, 13.97 Å, and 13.06 Å, respectively. The low-anglereflections showed second submultiples at 8.30 Å, 7.97 Å, 7.34 Å, and6.48 Å. The PXRD also exhibited higher submultiples of the low-anglereflections at higher 2θ values. The appearance of the submultiples isconsistent with Ni-AC having crystallized in a layered structure.

The IR spectrum of the Ni(0.5)-AC is provided in plot (b) of FIG. 2 andshows various stretching and bending vibrations. The vibrations at 2904cm⁻¹ and 2847 cm⁻¹ arise from stretching modes of C—H of the adamantanecarboxylate ion. Symmetric and antisymmetric vibrations of COO⁻groups ofadamantane carboxylate are seen at 1566 cm⁻¹ and 1489 cm ¹. The multiplestretching and bending modes less than 1000 cm ⁻¹ arise frommetal-oxygen bonds. A broad hump with a sharp peak at 3449 cm⁻¹indicates the presence of hydrogen-bonded hydroxy ion in the compound.The vibration at about 1600 cm⁻¹ is believed to arise from a bendingmode of water molecules and to indicate that the Ni(0.5)-AC has somewater present.

Thermal stability of Ni(0.5)-AC was studied using TGA. The TGA data areprovided as plot (b) of FIG. 3. The mass loss (˜8 wt. %) around 60° C.is mainly attributed to the physisorbed water. The material showsgradual but steady mass loss of around 7 wt. % from 60° C. to 320° C.,possibly as a result of small amounts of amorphous impurities present inthe sample. The TGA shows a massive mass loss of around 70 wt. % in therange of 320° C. to 420° C. accounting for hydroxyls, carboxylates, H,and C of the Ni(0.5)-AC. In total, Ni(0.5)-AC loses around 90 wt. % from25° C. to 800° C., leaving only 10 wt. % residue.

The Ni(0.5)-AC shows a layered morphology with tendency of layers togrow rods, as evident from the SEM images in FIGS. 8A-8D of the samematerial at different levels of magnification.

Example 4 Nickel Oxide from Thermal Decomposition of Nickel AdamantaneCarboxylate Salts

Similar to how Co-AC yields oxides of cobalt on thermal decomposition,Ni-AC was expected to give oxides of nickel on a carbon support uponthermal decomposition. The Ni(0.5)-AC prepared according to Example 3was decomposed from 25° C. to 450° C. for 4 h under air atmosphere. Asillustrated in plot (b) of FIG. 7, the PXRD spectrum of the resultantoxide residue exhibited reflections at 2θ angles of 37.21°, 43.23°, and62.9°, corresponding to 2.41 Å, 2.09 Å, and 1.47 Å, respectively. Basedon comparisons with literature values, the nickel oxide residue wasassigned to a NiO phase. The broad hump observed in the PXRD of Co₃O₄(plot (b) of FIG. 1) is missing in NiO. Without intent to be bound bytheory, it is believed that the absence of the broad hump may imply that(a) NiO does not have any carbon at all in it; or (b) the hump may havebeen obscured under the background of high-intensity reflections of NiO.

The template effect of incorporated adamantane observed in the formationof spongy, porous Co₃O₄ was expected for NiO as well. The SEMmicrographs of NiO resulting from Ni(0.5)-AC (FIGS. 9A and 9B) portray ananowhisker morphology. Individual crystallites of spherical NiO arearranged as nanowhiskers with micron length. Such an arrangement isbelieved to result in the highly porous nature of the nickel oxide.Without intent to be bound by theory, it is believed that the tendencyof Ni-AC to form rod-like shapes, possibly owing to the arrangements ofadamantanes, may give rise to the observed formation of highly porousnanowhiskers of NiO on thermal decomposition of the Ni-AC.

A qualitative elemental analysis of the NiO was undertaken using EDX.Integrated EDX spectra indicated the presence of Ni and 0 of the NiO ina molar ratio of about 1:1. The EDX spectra included also a peakattributed to elemental carbon. It is believed that the source of thecarbon is the adamantane moiety from the Ni-AC material.

Nickel oxide obtained from Ni-AC was further characterized by TEM (FIGS.10A-10D). The bright-field images of FIGS. 10A and 10B illustrate thetendency of NiO grow as whiskers having micron lengths. The selectedarea electron diffraction pattern of the nickel oxide derived fromNi(0.5)-AC in FIG. 10C is consistent with those reported in theliterature for NiO. A high-resolution TEM (HRTEM) image of the nickeloxide in FIG. 10D illustrates lattice fringes of rock-salt structuredNiO planes. In addition, the HRTEM shows the larger lattice fringeshaving d-spacings of approximately 1 nm that are not attributable to anyNiO plane. These lattice fringes with higher d-spacing may be assignedto carbons of the adamantane carboxylate that remain present in theoxide residue.

Example 5 Synthesis and Characterization of Copper AdamantaneCarboxylate Salts

Cu-adamantane carboxylate was synthesized by treating Cu(OH)₂ and1-adamantane carboxylic acid under hydrothermal conditions at 110° C.Prior to the reaction, the reactants were stirred for 1 h on themagnetic stirrer to achieve intimate mixing. Two Cu-AC compounds weresynthesized with different molar ratios of Cu²⁺ to ACA to evaluate theeffects of supersaturation on phase formation and the morphology of theresultant phase. A first compound, Cu(0.5)-AC, was synthesized using a0.5 molar ratio of Cu²⁺ to ACA. A second compound, Cu(1.0)-AC, wassynthesized using a 1.0 molar ratio of Cu²⁺ to ACA. The compounds werecharacterized by PXRD, IR, and SEM.

The PXRD pattern of Cu(0.5)-AC in plot (a) of FIG. 11 shows severallow-angle reflections, each of which is split into multiple peaks. Afirst reflection exhibits peaks corresponding to d-spacings of 13.32Åand 13.04 Å; a second reflection exhibits peaks corresponding tod-spacings of 11.25 Å, 11.11 Å, and 10.87 Å; a third reflection exhibitspeaks corresponding to d-spacings of 9.46 Å and 9.26 Å; and a fourthreflection exhibits peaks corresponding to d-spacings of 7.84 Å and 7.68Å. Higher-order reflections are present in a first group of peakscorresponding to d-spacings of 6.70 Å and 6.58 Å; in a second group ofpeaks corresponding to d-spacings of 5.65 Å, 5.52 Å, and 5.44 Å; and ina third group of peaks corresponding to d-spacings of 4.74 Åand 4.63 Å.These kinds of reflections in PXRD may be attributed to a compound thatis: (a) layered in nature or (b) having interstratifications, that is,intergrowths of one phase with another. In addition to thesereflections, Cu(0.5)-AC shows several low intensity reflections athigher 2θ values.

The IR spectrum of the Cu(0.5)-AC in plot (c) of FIG. 2 exhibits variousstretching and bending vibrations. The vibrations at 2901 cm⁻¹ and 2844cm⁻¹ arise from stretching modes of C—H bonds of adamantane ions.Symmetric and antisymmetric vibrations of COO⁻ groups of adamantane arepresent at 1573 cm⁻¹ and 1448 cm⁻¹. The multiple stretching and bendingmodes less than 1000 cm⁻¹ arise from metal-oxygen bonds. A broad featureat 3418 cm⁻¹ indicates the presence of a hydrogen-bonded hydroxyl ion inthe compound. The vibration at 1659 cm⁻¹ is believed to arise from abending mode of water molecules and is believed to indicate that Cu-AChas some water.

In the TGA plot (c) of FIG. 3, Cu(0.5)-AC shows a three-step mass lossunder air from 25° C. to 800° C. This behavior is similar to that oflayered double hydroxide materials. In the TGA study, the Cu(0.5)-AClost about 85 wt. % of its mass over the range of 25° C. to 800° C.,leaving about 15 wt. % oxide residue.

The morphology of Cu(0.5)-AC was evaluated by SEM. In the micrographs ofFIGS. 12A and 12B, the Cu(0.5)-AC shows a morphology in whichcrystallites have grown as rectangular shapes. It is believed that thecrystallite shapes indicate that Cu(0.5)-AC may have crystallized in amonoclinic crystal system.

The PXRD pattern of Cu(1.0)-AC in plot (b) of FIG. 11 is similar to thePXRD pattern of Cu(0.5)-AC in plot (a) of FIG. 11. However, a splittingof the basal reflection observed in Cu(0.5)-AC was not observed in theCu(1.0)-AC. It is believed that the absence of the splitting of thebasal reflection implies absence of interstratification in Cu(1.0)-AC.The intensities of the basal reflections were observed to be greater inthe case of Cu(1.0)-AC, suggesting more ordered crystal growth.

As evident from the SEM micrographs of FIGS. 12C and 12D, the Cu(1.0)-ACwas observed to have a fibrous morphology, different from therectangular crystals observed with Cu(0.5)-AC. It is believed that thelower concentration of adamantane carboxylate in Cu(1.0)-AC compared toCu(0.5)-AC has a definite effect in facilitating higher levels ofcrystal growth and changes in the morphology of the Cu(1.0)-AC material.

Example 6 Copper Oxide from Thermal Decomposition of Copper AdamantaneCarboxylate Salts

The Cu(0.5)-AC prepared according to Example 5 was decomposed at 450° C.for 4 h under air atmosphere. The resultant oxide material wascharacterized by PXRD, SEM, EDX, and TEM.

The PXRD pattern of resultant copper oxide in plot (c) of FIG. 11exhibits reflections at 2θ angles of 29.29°, 31.95°, 35.14°, 36.11°,38.26°, 41.96°, 43.10°, 48.35°, 53.02°, 57.81° and 61.10°, whichcorrespond to d-spacings of 3.04 Å, 2.79 Å, 2.55 Å, 2.48 Å, 2.35 Å, 2.15Å, 2.09 Å, 1.88 Å, 1.72 Å, 1.59 Å, and 1.51 Å, respectively. The phaseidentification of the resultant copper oxide revealed that majority ofthe copper oxide is CuO. The peaks at 2.48 Å, 2.15 Å, and 10.9 Å areattributable to Cu₂O, however. Thus, it is believed that resultant oxidehas a mixture of both CuO and Cu₂O. The mixture of copper oxides may becaused by uncontrolled decomposition of the precursor Cu(0.5)-AC.

The SEM micrographs of FIGS. 13A-13D illustrate the morphology of thecopper oxide obtained from the Cu(0.5)-AC. Thermal decomposition ofCu-AC compounds was expected to provide mesoporous nano-oxides of coppersupported on the carbon of the adamantane carboxylate residue. Asevident from the SEM micrographs of FIGS. 13A and 13B, the CuO includedfine crystallites in the nanometer range that were distributed on thelarge sheets having lengths of greater than 10 μm. The intercalatedadamantane carboxylate on decomposition grew as large sheets of carbon,on which copper oxides crystallites formed. The copper oxidecrystallites are particularly evident in the SEM close-up micrographs ofFIGS. 13C and 13D.

The nature and composition of the sheets and finer crystallites in theCuO was further characterized by EDX. EDX scans were conducted on areasof the large sheets and of the finer crystallites in the decomposedsample. By EDX, the sheet-like portion of the thermally decomposedCu(0.5)-AC was observed to have a percentage of carbon atoms that wasmuch greater than that of Cu and 0 atoms. The EDX spectrum of finercrystallites of the thermally decomposed Cu(0.5)-AC exhibited an amountof Cu and O substantially greater than that of carbon. The EDX spectraof both the sheet-like portion and the crystallites indicated thepresence of significant amount of carbon. The distribution of the carbonin the sample was further characterized by elemental mapping. In theelemental mapping, the residual carbon was found to be distributedhomogeneously throughout the sample.

The tendency of the copper oxide to grow as sheets on the carbon residueof adamantane was further confirmed by TEM images (FIGS. 14A and 14B). Aselected-area electron diffraction pattern (FIG. 14C) was consistentwith observations made from PXRD and SEM. The HRTEM image of the copperoxide in FIG. 14D showed lattice fringes having d-spacings matchingthose reported in the literature.

Example 7 Cobalt Oxide from Thermal Decomposition of Cobalt AdamantaneCarboxylate Salts

The Co(0.5)-AC prepared according to Example 1 was decomposed at 450° C.for 4 h under H₂ atmosphere. The resultant oxide material wascharacterized by PXRD, SEM, EDX, and TEM.

Generally, thermal decomposition of cobalt compounds would result in theformation of oxides of cobalt such as Co₃O₄ and CoO. In Example 7, thecobalt completely reduced to its metallic form and the intercalatedadamantane carboxylic acid fused to form long chains of diamondoids. ThePXRD pattern of resultant cobalt oxide in the plot of FIG. 15 exhibitsreflections at 2θ angles of 5.30°, 13.9°, 41.78°, 44.50°, 47.61°,51.66°, and 62.73°, which correspond to d-spacings of 16.6 Å, 6.36 Å,2.16 Å, 2.03 Å, 1.90 Å, 1.76 Å, and 1.47 Å, respectively. Thereflections at 5.3 and 13.9° 2θ are attributed to the long chaindiamondoids that resulted from the melding of the adamantane carboxylicacid. A close examination of the remaining reflections revealed thecrystallization of cobalt in two forms: hexagonal and cubic. Thereflections at 2θ angles of 44.5° and 51.66° are assigned to the cubiccobalt phase, and reflections at 2θ angles of 41.78°, 44.5°, 47.61°,62.73° are assigned to hexagonal cobalt phase. The reflection at 44.5°2θ and the corresponding d-spacing 2.03 Å was common to both the formsof the cobalt, the hexagonal and the cubic.

The continued presence of adamantane inside the galleries of the formednanocomposite was characterized using IR spectroscopy as shown in FIG.16. The vibrations due to the COO⁻group and C—H group are seen at 1736cm⁻¹, 1437 cm⁻¹, and 3014 cm⁻¹, 2944 cm⁻¹ respectively. These vibrationsindicated the continuous presence of adamantane ion in the resultantnanocomposite. The vibration at 1217 cm⁻¹ is assigned to the (C—O)stretch of the adamantane ion. Additionally, FIG. 16 showed a weak broadvibration centered around 3464 cm⁻¹ from the hydrogen bonded hydroxylions.

The SEM micrographs of FIGS. 17A-17D illustrate the morphology of thecobalt oxide obtained from the Co(0.5)-AC. Thermal decomposition ofCo-AC compounds was expected to provide mesoporous nano-oxides of cobaltsupported on the carbon of the adamantane carboxylate residue.

The tendency of the cobalt oxide to grow as sheets on the carbon residueof adamantane was further confirmed by TEM images (FIGS. 18A-18D). Theselected-area electron diffraction pattern (FIG. 18D) evidenced cobaltmetal nanoparticles on the chains/sheets of diamondoids.

Example 8 Copper Oxide from Thermal Decomposition of Copper AdamantaneCarboxylate Salts

The Cu(0.5)-AC prepared according to Example 5 was decomposed at 450° C.for 4 h under H₂ atmosphere. The resultant oxide material wascharacterized by PXRD, SEM, EDX, and TEM.

The PXRD pattern of resultant copper oxide in FIG. 19 exhibitsreflections at 2θ angles of 5.4°, 13.76°, 42.93°, and 50.06°, whichcorrespond to d-spacings of 16.35 Å, 6.43 Å, 2.10 Å, and 1.82 Å,respectively. The peaks at 2.10 Å and 1.82 Å are attributable tometallic copper nanoparticles, however. The reflections at 2θ angles of5.4° and 13.76° (as shown in the inset plot (b)) are similar to the oneobserved in Example 5, the Cu-diamondoid nanocomposite and are assignedto the diamondoids. The phase identification of the resultant copperoxide revealed that majority of the copper oxide was CuO. Thus, it isbelieved that resultant oxide has a mixture of both CuO and Cu₂O.

The continued presence of adamantane inside the galleries of thenanocomposites was characterized by IR spectroscopy (FIG. 20). Thevibrations of the (COO⁻) groups appear at 1733 cm⁻¹, 1443 cm ¹, and thevibrations of the C—H groups appear at 3010 cm⁻¹, 2941 cm⁻¹. Thesevibrations confirm the presence of adamantane ion in the composition ofExample 8. The vibration at 1224 cm⁻¹ arises from the (C—O) stretch ofthe adamantane ion. The IR spectra showed a weak broad vibrationcentered around 3460 cm⁻¹, arising from the hydrogen bonded hydroxylions.

The SEM micrographs of FIGS. 21A-21D illustrate the morphology of thecopper oxide obtained from the Cu(0.5)-AC. Thermal decomposition ofCu-AC compounds under a reducing atmosphere was expected to providemesoporous nano-oxides of copper supported on the carbon of theadamantane carboxylate residue. Under the reducing atmosphere, thedecomposition of the Cu-AC was controlled and yielded a nanocomposite.

The morphology and composition of the sheets and finer crystallites inthe CuO were further characterized by EDX. EDX scans were conducted onareas of the large sheets and of the finer crystallites in thedecomposed Sample 8. The distribution of the carbon in the sample wasfurther characterized by elemental mapping (FIGS. 23A-23D). In theelemental mapping, the residual carbon, oxygen and copper weredistributed homogeneously throughout the sample. This homogeneousdistribution of constituent components indicates the formation of thenanocomposite from the molecular level. TEM micrographs FIGS. 22A-22Dfurther supported the characterizations from SEM, EDX, STEM and HRTEM.

In a first aspect, the disclosure provides a method for preparing atransition metal nanocomposite, the method comprising: mixing atransition metal hydroxide and a diamondoid compound having at least onecarboxylic acid moiety to form a reactant mixture; hydrothermallytreating the reactant mixture at a reaction temperature for a reactiontime to form a transition-metal adamantane carboxylate salt; andthermally decomposing the transition-metal adamantane carboxylate saltin a reducing atmosphere at a decomposition temperature for adecomposition time to form the transition metal nanocomposite.

In a second aspect, the disclosure provides the method of the firstaspect, in which the diamondoid compound is 1-adamantane carboxylic acidand the transition metal hydroxide has an oxidation state of M+2, whereM is chosen from cobalt (Co), copper (Cu), or combinations of cobalt andcopper.

In a third aspect, the disclosure provides the method of the first orsecond aspects, in which the transition metal hydroxide and the1-adamantane carboxylic acid are mixed in amounts that provide a molarratio of M²⁺ to 1-adamantane carboxylic acid in the reaction mixture offrom 0.5:1 to 1:1.

In a fourth aspect, the disclosure provides the method of any of thefirst through third aspects, in which the reaction temperature is from100° C. to 180° C.

In a fifth aspect, the disclosure provides the method of any of thefirst through fourth aspects, in which the transition metal hydroxide isCo(OH)₂ and the reaction temperature is 110° C.

In a sixth aspect, the disclosure provides the method of any of thefirst through fifth aspects, in which the transition-metal hydroxide isCu(OH)₂ and the reaction temperature is 110° C.

In a seventh aspect, the disclosure provides the method of any of thefirst through sixth aspects, in which the reaction time is at least 12hours.

In an eighth aspect, the disclosure provides the method of any of thefirst through seventh aspects, in which thermally decomposing thetransition metal adamantane carboxylate salt further comprises heatingthe transition metal adamantane carboxylate salt from room temperatureto the decomposition temperature at a rate of 5° C. per minute, andwherein the decomposition temperature is at least 450° C.

In a ninth aspect, the disclosure provides the method of any of thefirst through eighth aspects, in which the decomposition time is atleast 4 hours.

In a tenth aspect, the disclosure provides the method of any of thefirst through ninth aspects, in which the transition metal nanocompositecomprises transition metal oxide particles.

In an eleventh aspect, the disclosure provides the method of any of thefirst through tenth aspects, in which transition metal nanocompositecomprises from 70 wt. % to 80 wt. % metal oxide and from 20 wt. % to 30wt. % carbon, based on the total weight of the transition metalnanocomposite.

In a twelfth aspect, the disclosure provides the method of any of thefirst through eleventh aspects, in which the transition-metal adamantanecarboxylate salt comprises Co-AC.

In a thirteenth aspect, the disclosure provides the method of any of thefirst through twelfth aspects, in which the cobalt oxide comprises CoO,Co₃O₄, or a mixture of CoO and Co₃O₄.

In a fourteenth aspect, the disclosure provides the method of any of thefirst through thirteenth aspects, in which the transition-metaladamantane carboxylate salt comprises Ni-AC.

In a fifteenth aspect, the disclosure provides the method of any of thefirst through fourteenth aspects, in which the transition metalnanocomposite comprises crystallites of NiO configured as porousnanowhiskers.

In a sixteenth aspect, the disclosure provides the method of any of thefirst through fifteenth aspects, in which the transition-metaladamantane carboxylate salt comprises Cu-AC.

In a seventeenth aspect, the disclosure provides the method of any ofthe first through sixteenth aspects, in which the transition metalnanocomposite comprises carbon sheets and nanoparticles of copper oxidesupported on carbon sheets.

In an eighteenth aspect, the disclosure provides the method of any ofthe first through seventeenth aspects, in which the copper oxidecomprises CuO, Cu₂O, or a mixture of CuO and Cu₂O.

In a nineteenth aspect, the disclosure provides a catalyst systemcomprising the transition metal nanocomposite is prepared according toany one of the first through eighteenth aspects.

In a twentieth aspect, the disclosure provides a method for catalyzing achemical reaction between at least one first reactant and at least onesecond reactant, the method comprising: reacting the at least one firstreactant and at least one second reactant in the presence of a catalystsystem according to any of the first through nineteenth aspects.

In a twenty-first aspect, the disclosure provides for an electrodecomprising the transition metal nanocomposite prepared according to anyone of the first through twentieth aspects.

In a twenty-second aspect, the disclosure provides for a cathode or ananode comprising the transition metal nanocomposite prepared accordingto any one of the first through twenty-first aspects.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the embodiments described inthis specification without departing from the spirit and scope of theclaimed subject matter. Thus it is intended that the specification coverthe modifications and variations of the various embodiments described inthis specification provided such modification and variations come withinthe scope of the appended claims and their equivalents.

What is claimed is:
 1. A method for preparing a transition metalnanocomposite, the method comprising: mixing a transition metalhydroxide and a diamondoid compound having at least one carboxylic acidmoiety to form a reactant mixture; hydrothermally treating the reactantmixture at a reaction temperature for a reaction time to form atransition-metal adamantane carboxylate salt; and thermally decomposingthe transition-metal adamantane carboxylate salt in a reducingatmosphere at a decomposition temperature for a decomposition time toform the transition metal nanocomposite.
 2. The method of claim 1,wherein the diamondoid compound is 1-adamantane carboxylic acid and thetransition metal hydroxide has an oxidation state of M+2, where M ischosen from cobalt (Co), copper (Cu), or combinations of cobalt andcopper.
 3. The method of claim 2, wherein the transition metal hydroxideand the 1-adamantane carboxylic acid are mixed in amounts that provide amolar ratio of M²⁺ to 1-adamantane carboxylic acid in the reactionmixture of from 0.5:1 to 1:1.
 4. The method of claim 1, wherein thereaction temperature is from 100° C. to 180° C.
 5. The method of claim1, wherein the transition metal hydroxide is Co(OH)₂ and the reactiontemperature is 110° C.
 6. The method of claim 1, wherein thetransition-metal hydroxide is Cu(OH)₂ and the reaction temperature is110° C.
 7. The method of claim 1, wherein the reaction time is at least12 hours.
 8. The method of claim 1, wherein thermally decomposing thetransition-metal adamantane carboxylate salt further comprises heatingthe transition-metal adamantane carboxylate salt from room temperatureto the decomposition temperature at a rate of 5° C. per minute, andwherein the decomposition temperature is at least 450° C.
 9. The methodof claim 1, wherein the decomposition time is at least 4 hours.
 10. Themethod of claim 1, wherein the transition metal nanocomposite comprisestransition metal oxide particles.
 11. The method of claim 10, whereinthe transition metal nanocomposite comprises from 70 wt. % to 80 wt. %metal oxide and from 20 wt. % to 30 wt. % carbon, based on the totalweight of the transition metal nanocomposite.
 12. The method of claim 1,wherein the transition-metal adamantane carboxylate salt comprisescobalt adamantane carboxylate.
 13. The method of claim 12, wherein thecobalt adamantane carboxylate comprises CoO, Co₃O₄, or a mixture of CoOand Co₃O₄.
 14. The method of claim 1, wherein the transition-metaladamantane carboxylate salt comprises Ni-AC.
 15. The method of claim 14,wherein the transition metal nanocomposite comprises crystallites of NiOconfigured as porous nanowhiskers.
 16. The method of claim 1, whereinthe transition-metal adamantane carboxylate salt comprises Cu-AC. 17.The method of claim 16, wherein the transition metal nanocompositecomprises carbon sheets and nanoparticles of copper oxide supported oncarbon sheets.
 18. The method of claim 17, wherein the copper oxidecomprises CuO, Cu₂O, or a mixture of CuO and Cu₂O.
 19. A method forcatalyzing a chemical reaction between at least one first reactant andat least one second reactant, the method comprising: reacting the atleast one first reactant and at least one second reactant in thepresence of a catalyst system comprising the transition metalnanocomposite prepared according to claim
 1. 20. An electrode comprisingthe transition metal nanocomposite prepared according to claim 1.